| The increase of the penetration of renewable energy in household environment and the application of dc appliances have lead to the gradual rise of the intelligent residence adopting dc power distribution systems.And the topologies used to achieve the high efficient integration between the sources and loads in dc house have become the researching focus.Generally,several two-port dc/dc converters are employed in traditional integration topologies based on common dc bus,which results in complex and discrete system structure,high hardware construction cost,large system power conversion losses and low reliability.Multiport converter can effectively overcome the disadvantages above,so it has a broad application prospects in dc residence.And the topology and control method of it are keys to the current research.To solve the problems above,a novel partially isolated multiport converter named PIMPC with six bidirectional ports is put forward in this thesis.The grid,PV power generation system,energy storage and dc residential loads can be integrated into the proposed converter efficiently while three different supplied voltages can be provided for loads.Besides,a multi-objective control strategy is presented for PIMPC to achieve multiple control objectives such as ensuring the stability of the supplied voltages,maximizing the utilization of PV,avoiding the overcharge/overdischarge of energy storage,maintaining system power balance and reducing the power exchange between dc house and the grid.The main contents and achievements of this paper are as follows:1.According to the requirements of the MPC applied in dc house,a novel partially isolated multiport conveter(PIMPC)consist of four full-bridge units,two bidirectional buck/boost units and a high-frequency four winding transformer is presented.The topology and the equivalent circuit of PIMPC are described in detail,as well as the operation principle which includes the operation modes,the commutation process and the power flow control model.And the theoretical analysis is verified through open-loop simulation.2.On the basis of the introduction of residential dc microgrid system which contains power grid,grid-connected bidirectional rectifier,PV power generation system,energy storage,residential loads and the core components PIMPC,the corresponding system control targets are given.And the system control strategies are developed as follows: a)The proposed multi-objective control is adopted for PIMPC;b)MPPT control is used for the boost converter in PV power generation system;c)The voltage and current double closed-loop control is employed for the grid-connected bidirectional rectifier.Among them,the proposed multi-objective control strategy is the focus.3.Taking an ordinary residence in China as an example,a dc residential system case is designed.The power of typical residential loads is calculated,and the power level of the dc residential system is determined accordingly.On the basis of this,the capacity of PV panels and enegy storage is designed,as well as the port voltage and power of PIMPC and the revelant components parameters in its main circuit.4.Based on the designed dc residential system case,a corresponding system simulation model is established in Matlab and several operation conditions of it are simulated.The simulation results indicate that the proposed PIMPC and multi-objective control can effectively realize the predetermined control targets,and then the feasibility and effectiveness of the proposed topology and control strategy are verified. |
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